1. Field of the Invention
The present invention relates generally to self-oscillating drivers, and relates more particularly to self-oscillating drivers with fault protections.
2. Description of Related Art
Transistor drivers are used in a number of applications including full-bridge and half-bridge switching arrangements used to drive a load. For example, full-bridge circuits are used to operate DC-Bus converters, HID lamps and other well known industrial applications. Half-bridge drivers are also used for DC-DC converters and fluorescent lamps.
The above types of applications may incorporate a driver that uses an oscillating signal to provide switching pulses to the full or half-bridge circuits. During startup conditions, the oscillator operates at a frequency that provides signals to gate drivers, for example, to immediately begin switching the full or half-bridge switches at startup. This type of immediate startup operation can have an impact on the ruggedness of the full or half-bridge switching components, that is, numerous startup conditions of this type can result in deterioration of the characteristics of the components and lead to unwanted circuit failures.
In a number of the applications discussed above, the full or half-bridge switching circuits drive a primary side of a load, to transfer power to a secondary side of a load, such as through a transformer. In the event of an overcurrent condition, the full or half-bridge switching circuit can be disabled to prevent component failure or damage, on either the primary or secondary side of the load. Previous full and half-bridge driver circuits provide automatic restarts in the event of an overcurrent event to attempt to operate the circuit once a fault condition has been removed. In these instances, an automatic restart can occur before the full or half-bridge circuit has recovered from the overcurrent stress.
It would be desirable to provide a full or half-bridge driver with a soft start feature and to protect against overcurrent conditions.